When Creating an Autofill by Title and Entries as Data Source, Please add Selected Search Result Entry itself as a Source of Autofill Source.
This will allow to Search, Link an Entry and also Autofill relevant Data from that entry from single Text Box.

For Example, Library Order has "Customer Search" as Text Field and "Customer" as Link to Entry" and also has Fields like "Address" to Autofill.
We setup autofill from Library Customer and "Customer Search" is Input Field to search.
User can quickly search customer by typing and Autocomplete Fields like Address are getting Filled, but Link to Entry Field named Customer still has to be selected manually again, as there is no option to map the Search result itself to a Link to Entry Field.

If such feature is provided user can quickly search and link fields.